1. Field of the Invention
The present invention relates to a secondary battery that includes a gas release valve.
2. Description of Related Art
Research into and development of hybrid and electric vehicles equipped with secondary batteries have been pursued with increasing vigor as a way of addressing various environmental issues in recent years. Since heat may be generated in a secondary battery due to an abnormality, resulting in an increase in battery internal pressure, secondary batteries assuming structures that include a gas release valve have been proposed as a safety measure.
For instance, Japanese Patent Official Gazette No. 4155734 discloses a sealed battery that includes a gas release valve constituted of an area defined by a surrounding groove that is formed at a sealing plate closing off an opening. A safety valve of the battery disclosed in Japanese Patent Official Gazette No. 3222418 includes a circular fracturing groove and a fracture-starting groove formed in an area further inward relative to the fracture groove.